Telephone system



TELEPHONE SYSTEM Filed Feb. 24, 1930 2 Sheets-Sheet l A TTURNE) May 24; 1932. R. c. PAINE 1,859,385

TELEPHONE SYSTEM Filed Feb. 24, 1930 z Sheets-Sheet 2 /NVEN TOR RC. Fk/NE ATTORNEY Patented May 24, 1932 UNITEDSTATES ma ROBERT c. PAIN'E, or BOONTON, NEW. JERSEY, Assislvoa TQ- BELL TELEPHONE L mo- RATORIES, INcoRroRn'rEn, or NEW YORK,'1T. Y., A CORPORATION or NEW Yom:

TELEPHONE svsrnivr Application filed February 24,1930. Serial No. 430,561.

This invention relates to telephone systems and particularly to trunking arrangements for extending connections from .onestation or'officeto a: distant office. 1 i

The objects of the invention are to effect an economyin the use of equipment and especially in the use of interofiice trunks, to

improve the efficiency of these trunks, to simp'lify the signaling equipment, and to other- 1 wise improve systems of the characterymen tioned.

In systems involving differentcla sses of lines,'it has been the practice in the past to group or segregate lines according to'classes 1 in such a manner that calling lines of one class are extended to an operators position over trunks of one group,- whereas the calllng linesof another classare extended to the same or another operators position over trunks of a difi'erent group. In, this way, the operator'is aware of the class -to which the calling linebelongs and knows accordingly how to dispose of the call and what method to use in charging for the service.

' In other instances, class-of-service informationhas-been given the operator by means "of distinctive signals, which inform her asto the nature of each calling linethat is extended to her position. This is usually ac- '30 complished by providing the subscribers lines with some identifying means which, when a call is made, so affects the circuits involved in extending the connectionthat one kind of signal'is given the operator when a line of one class calls and another kind when a line of another class calls. 7 I According to the present invention, an advantage is secured over these prior arrangemonts by means of a system in which calling lines of-two different classes are extended to an'operators position over trunks of the same group, the. lines of one class having access to said trunks directly through line switches and the lines of the other'cl'ass having access to said trunks through one or moreselector switches. The circuits are so arranged that thesignal, which is given the operator, "differs according to whether the trunk leading to switch or througha selector'switch,

her position-is seized directly through a line" A feature of the invention is a system in which the discriminating-signal received by the operator is effected by a signal device, such i as a lamp which is lighted'steadily under control of a circuit includingtlie talking conducalso be use'd'by the operator: forexten'ding calls in the opposite direction.

tors of a two-wire interofiice trunk when the 5 In the'drawings, Fig. 1 discloses a' local or I community ofiicehaving a-two-way trunk circult which extends to an operatorsposition iii-la distantcentral office. This figure also shows subscribers lines'of difierent classes and switches for connecting said lines tothe' trunk circuit. It also diagrammatically il lustrates selector and connector switches for completing incoming calls. thepther end of the two-way trunk circuit terminating at an operators position in the centralo'ffice. i W

In small communities where lines of different classesare involved such-'as;flat rate lines and coin .box lines,-thetratiic' may be Fig. ,2 shows" such that it is inefficient to provide separate,

trunk circuits tov handle the calls from each of the different classes of lines; on theother .hand,it is necessary to provide some way of as j advising the operator "who receives the calls I as to the classofthe calling line. For in: stance, if the call isfrom acoin box line she must know this and be able to'supervis'e the deposit and disposition of the coins; In'the present system, this requirementis accom V plished by taking advantage of the'factr that lines of diiferent classes, although extended to-the same operators position over the same trunk circuit, must be connected to the-out:

going end of the trunk circuit over, different;

paths.v Thejline 100, for instance, may be'a fiatjrate line and is extendedto thetru nk circuit T over an ordinary rotary .line; switc1i.; p

102 and through a directively operable selector switch S. In other words, the subscriber on initiating a callfirst causes the switch 102 to operate to extend the line to the selector S. He is then required to dial some digit such as the digit to cause the selector S to seize the outgoing end of the trunk circuit T. Seizure of the trunk T will cause a trunk h lamp 214 at't-he distant manual operators position to light steadily, advising the operator that a call is awaiting on the trunk T and that the calling line is one of the flatrate class. Again if a coin line 101 initiates a call, the line is extended over a line switch.

107 directly to the outgoing end of the trunk T without requiriiw an further actionon the i I h v I part of the callingsubscriber. In this case,

however, the line switch 107 is arranged to affect the trunk circuit T in such a manner that the trunk signal 214 at the operators position will be flashed to advise her that the call awaiting her attention is one from a coin-box line. i

- For calls incoming to the community ofiice 1 from the central office, trunlr circuit T is so arranged that the operator can seize the trunk atthe centraloflice and transmit dial impulses to-the community oflice, causing the setting of selector and connector switches such as the switches S'1 and C to complete the connection to a desired subscribers line 140. I r r A detailed description will now be given, and, for this purpose, it will first be assumed that the subscriber of line desires to make a central office call. In response to the ini.-

tiation of the call, switch 102 operates to extend the line over brushes 103, 104, and 105 to "the selector switch 'S. The subscriber thereupon manipulates his dial 141 to send a series of impulses to the selector switch S, causing it toposition-its brushes 116,117, and 118 on the terminals of the trunk circuit T.

As soon as the trunk is seized, relay 127 operates in a circuit from battery throughits rightwinding, next to the outer upper arma- .tial over conductor 142 for starting the ringing machine (not shown), which may. also serve to drive the interrupter 133. Relay 128 also causes the operation of relay 124; in

a circuit from battery throughthe winding of the latter relay, outer rightbaclrjcontact of relay 131, right contact of relay 127, conductor 143 to ground at the inner left contact of relay 128. Relay124 locks to the ground ed conductor 144. Slow-release relay 134 is also operated in a circuit through its winding, middle left armature andback contact of relay 131, right contact of relay127 to the grounded conductor 143. 1 Relay 124 shifts the circuit of relay 127 so that it now extends from battery through the right winding of relay127- next to the uppermost"armature and front contact of'relay 124, upper left winding of repeating coil 123, uppermost armature and front contact of relay 124, thence over the subscribers line and returning through the lowermost armature and front contact of relay 124, lower left-winding of the coil .123, next to the lowermost armature and front contact of relay 124 to ground through the left winding "of relay 1'27 The difference is that the circuit nowincludes the left windings of the repeating coil 123 Relay 124 at its uppermost and lowermost armatures disconnects the trunk circuit T from the branch 139 leadingto the selector switch S1. Relay 124 also causes the operation of relay135 in acircuit from battery through the winding of the latter relay to ground through the inner lower armature and con tact of relay 124; Relay135 at its lower ar- .mature connects =tl1'e-source145 to the repeat ing coil 123 to furnish a tone-current in the. calling subscribers line. Relay .135 also reverses the direction of current fiow over the trunk circuit T to the distant manualofiice.

trunk circuit T is so arranged that current of a lowrvalue normally flows throughthe windings of the relay 126 at the local office over the two-wire trunk circuit T to the manual office and through a bridgecircuit of high resistance thereat. The-circuit for this purpose may be traced frombattery through the left winding ofv relay 126, outer normal contact of relay 129, uppermost ice It may bewell to note at this point that the normal contact of relay 135, upper right" winding of coil 123-, l conductor 136,- thence to the distant central officethroughrthe lower left winding of repeating coil, 200, winding of relay 204,,conductor 2117, through the windings of the high resistance, polarized relays 21 2 and 213, conductor 218, upper left wi'nding of coil 200, lower normal contact of'relay V 207, conductor 137, through the lower right winding of coil 123, inner upper normal con tactof relay 135, inner normal contact ofv relay 129 to ground through the right Winding of-relay 126'.v The relays 212 and 213are so polarized that relay 212 is normally operate-d, whereas the relay 213 norma'lly has its armature retract-ed. Relay 126'at the local oflice is marginal and will not 'operateinrespouse to the small amount of current flow ing dueto the high resistance of: relays 212 and 213. Relay 204 at the icentralofiice also;

normally remains inert due to the high resistance of relays 212 and 213..

When, therefore, the slow-release re1ay-134 operates as above explained, the trunk circuit is modifiedto exclude the right windingsof the repeating coil 123 to improve the operat ing characteristics.

from battery through the left winding of conductor 136 and returning over conductor 137 through the inner front contact of relay 134', inner normal contact of'relay 135 and thence through the right winding of the relay 126. When later the relay 135 operates, as explained, it reverses the direction of current flow from the windings of relay 126 over a the conductors 136 and 137 The reversal of current over the trunk circuit causes the relay 212 to release and the relay 213 to operate. A circuit is now com pleted from ground through the back contact of relay 212, contact of relay 213, normal contacts and winding of relay215 to battery through the lower back contact of relay-216.

Relay'215 operates and looks through its winding and inner left front contactto ground at the back contact of relay 212. Relay215. completes a circuit for the lamp 214 traceable from battery through said lamp, outer left contact of relay 215, contacts of relays 213 and 212 to ground. The lamp lights steadily in this circuit to advise the operator that a call is awaiting on the trunk circuit T and that the callin'glineis of a given class. Relay 215 also closes a circuit from battery through the resistance 206, inner lower back contact of relay 203, conductor 219, inner right contact of relay 215, conductor220, winding of the sleeve relay 211 to ground. Relay 211 operates and causes the operation of relay 210 in a circuit from ground to the contact of relay 211, lower normal contact of relay 209, winding of relay 210 to battery. a

The operator at position 0 sees the lamp lighted and answers the call by inserting the answering plug 230 in the jack 201. It will be noted that trunk T, appears intwo' jacks 201 and 202. This double appearance isito enable the operatorto determine the nature of the calling line after having set up the connection. The ack 201 indicates that call ing line is of the flat-rate class, whereas the jack 202 identifies calling lines of the coinboX class. The insertion of the plug 230 in the jack 201 causes the operation of relay 203 in a-circuit from battery through the-lower left winding of repeating coil 221, winding.

. tact of relay 207..throughgthe-tip of the jack and plug and'the upperl'eft winding of coil a c 221to groundf FRelay f222 operates and {shunts the supervisory lamp 240, causing" of supervisory relay 222, ring of the plug and jack, right contact of relay 204, normal con-"- tact andwinding of relay 203, conductor 2277 to ground at the contact of relay 211. Relay 203 locks through its innerupper contactst'o;

Following the opera-- tion of relay 134, the circuit may be traced shunts the relays 212 and 213over a path-extendingfrom-theconductor 13,6, lower left the grounded conductor 227.. 1 Relay 203 1 winding .of. coil 200, winding of relay 2 04,

lowermost contact of relay 203, upper left;

winding of coil'200,lo wer normal contacts of relay 207 to the conductor 137. Relay213' now releases a-nd opens the'circuit of the lamp 214. Relay 20.3 also disconnects battery from V the lead'219. Relay 211 is now heldjover the sleeveof the plug and jack .to battery in the .cord' circuit. Relay 203 inyoperating causes the operation ofrelay 216inacircuit from battery through the resistance 206,.inne'r lowerfront contactof relay 203, conductor 234, Winding of relay 216-Eto ground at'the back contact of relay 212. 'Relay 216operates and locks to ground at the back contact, of

relay212. nRelay 216; releasesthe relay 215.:

: Relay 204 when freed fro-mthe resistance of relays 212and 213"oper'a'tes in series With the relay .126 atth'e local office. Relay'204 at its right contact opens a bridge'which would otherwise exist across the tip and ring con-. ductors of the trunk circuiton the right hand side of the repeating coil 200. 3 i

When the resistance of relays 212 and 213 is removed. at the central office, as above de- "scribed, relay-126 at the local ofiiceioperates.

anclcomplet'es a circuit from ground through its inner front contact, outer right. contact. zof relay 128, inner lef-t normal contact of relay. 131.to battery. Relay 131 operatesand" looks through itsinnerleft front contact,- conductor 143 to ground at'the inner left con- I tact'of relay 128. Relay 13.1[disco nnects the i tone source 145 and closes an opera-tingcircuit'for relay 129. This circuit maybe traced from battery to the winding of relay 129,

outer right front contact of relay 131, right ductor 143. Relay 129 in operating disconnects the windings ofrelay 126 from. the-l 1 contact of relay 127 to the grounded con-hi tip and ring conductors of the trunk circuit" tion to the called line with thefcalling. ack 231 conversation willnow take place.

Relay 204 at the central office in releasing completes-a circuit from battery through the lower left windingof the coil 221 the operators cordcircuit, winding of the relay; 222, ring oftheplug 230 and jack 201, right 1 contact of relay. 204, uppermost-front contact of relay 203, coil 205'Qupper1nost con .to extinguish: p

tic

do so by repeatedly operating: his switchhook. Thiscauses the'rela'y 127 to release and reo'perate, in turn causing the repeated operation and release of' rela-y 129 .Each time relay 1'29 releases, he relay 204 at the central oflice operates and opens the bridge across the trunk circuit, causing the release of the'supervisory relay 222 and the lighting 'vances the brushes another'step, andthis of the lamp 240. I V I AEfte r conversation has been completed, the calling subscriber replaces his receiver, causing the releaseof relay 1 27. :Relay 128, however, is held by means "of a circuit from battery through its winding, left armature and-back contact of relay 127 to ground at the innerleft frontfcont'actof relay 126.

,, Relay 127 releascs relay 129, which reconne'cts the windings of relay 126. to thetrunk circuit. This causes theoperation of relay 204, which opens thecir-cuit of rela -r222, causing the supervisory signal 240 to illuminate. Assoon asthe operator removes the plug230 from the jack 201, relay 211 releases and in turn releases relay 203. Assoon as relay 203 fully releases, it reoperates relay 2-11 in a circuit from battery over the con ductor 219, inner upper contact of relay 216, winding of relay 211 to ground. Relay203 v removes the shunt around the windings of relays 212 and213, whereupon relay 204 at the central cities and relay 126 at the local office-are released. I

When relay 126 releases, it opens the cirsuit of slow-release relay 128, which'a-fter an interval retracts its armatures. Relay 128 opens thejholding circuits of relays 131 and 124, and these relays release. Relay 124 in P turn releases relay 135, which restores the flow of current oyer the'trunk circuit to its normal direction. hen the" flow of current i is restored to its normal direction, relay 212 of relay pot'ential from the sleeve conductor 122 causes the release of the selector S andthe restoration of the system to its normal conditionu a 7 It will-next be assumedthat the calling party at the coin-box station 101' wishes to make a'central o'flice call; He initiates the "call by removing his receiver from the switchhook, whereupona circuit is completed from I battery through the upper winding of relay 113, uppermost normal contact of relay 114,

thenceoyer the loop of the calling line and returning through the lowermost normal contact :ofjrelay 114 7 and the lower winding of relay .113 to ground. .Relz'ty 11-3 "at its upperm'ostcontact places groundpotential on the sleeve conductor 149, to render theline Relay 2-12 on attracting its described in detail.

busy to connector switches. Rela y 113'also completes a circuit from ground througlrits uppermost contact, conduotor150, brush109 on its No. 1 contact,'inner upper back contact of relay 114, contact-and winding of the step ping magnet 115 to battery. The magnet 115 interrupts its own circuit and steps the brushes 108, 109, 110,111 and 112 to the next setv of terminals If the trunk appearing in these terminals is busy, the magnet115 adprocedure continues until the brush 109 reaches an ungrounded terminal representing an idle trunk circuit T. hen this occurs the relay 114 operates in a circuit from battery through the winding and contact of magnet 115 the Winding of relay 114,'conductor 149 to ground at the upper contact ofre lay 113. 7 Although this circuit has existed during the stepping oi the switch 1'07,the cutoii'relay-114 has been shunted so long as the wiper 109 encounters busy test contacts. Due] to the high-resistance of the cut-011' relay 114, the magnet 115 does not operate in' series therewith. Relay 114 immediately applies ground-potential to'the test conductor122 by 7 means of the'circuit from ground,upper contacts. 113,? conductor 149, inner upper front contact of relay 114'and brush 109. Relay 114 opens the circuit of relay 113, but this relayris slow to release; therefore, it does not immediately retract its armatures. v

As soon as relay 114 operates, it'eXten-dsthe tip and ring conductors of the line through to the tip and ring conductors ofthe trunk circuit T, and relay 127 operates in the manner hereinbefore described. Relay 127 operates relay 128, which returnsa ground potential overthe conductor 122 and the brush 109 to hold relay 114 operated when relay 113 subsequently releases. Acircuit is now completed for operating the relay 132, which serves to cause the flashing of lamp 214 at the operators position to advise her that the call originated on coin-box line. The circuit i or relay 132 may be traced from'battery through the winding 'ther'eof, middle. right contact of relay131,conduc'tor1150,"bruslr108 to. ground at the inner lower contact'of relay 114. Relay 132 closes a circuit from ground 1 5 through the interrupter 1233, contact of said relay through the winding :of relay 129 to battery. The interrupter 133 causes the relay 129. to repeatedly operate and release. This 126 from the trunk circuit, causing the re-v peated operation an d release of the polarized I relay 213and the'flashing of the lamp 214.-

The operator observing the flashing lamp knows that'the call has originated on a coin-" box line; accordingly she answers by insert ing the answering plug 230 in the aclr 202 oi the trunk. From this-point on, thecomple tion of the connection is the same as-already repeatedly disconnects the windings of relay The subsequent opera- 1.2av

2 tion of relay 131releases relay 132, which disconnects the-interrupter 133.

It will next be assumed that a subscriber in the central oflice wishes to obtain connection with a line in the local ofiice, such asthe subscribers line 140. The operator receives.

ground. Relay 211 operates the relay210 in an'obvious circuit. Relay 203 also operates in a circuitfrom ground over conductor 227 r through the winding and normal contact of relay 203 right contact of relay 204, over the ring of the jack and plug, lower normal con tacts of dialing key 233, winding of the relay 223, lower right .windingof coil 221 to battery. Relay 203 looks through its own contact under control of relay 211. Relay 203 shunts the relays 212, and 213 as hereinbefore explained,causing relay 212 to release and permitting relay 204 to operate in series with the windings of relay 126 at the distant local office. With relay 212 released and relay 203 operated, relay 216 operates as above explained. Relay 216 looks through its own contact to the contact ofrelay 212. a r

When the operator isready to transmit impulses, she throws the dial key 233, which connects the impulse dial 225 to the calling end of her cord circuit. As soon as thedial 225 is moved-ofi normal the lower contacts are closed, and relay 207 nowoperates in a circuit from-battery through its winding and normal contact, left contact of relay 204, through the ring of the jack and plug, lower closed contacts of key 233, ofi-normal contacts of the dial 225 to ground. Relay 207 looks through its own contacts to the ofl normal contacts of the dial 225. Re1ayf207 modifies the circuit incoming from the local ofiice so that it may now be traced over the conductor 136, resistance .208, upper back contactof relay 209, contact of relay 210,

lowermost front contact of relay 207 to con-' ductor 137. This bridge across the'trunk T shunts the relay 204, and-said relay releases. Relay 207 also operates relay 209 in an-obvious circuit. Relay 209 again modifies the circuit incoming from the local office so that it now excludes the resistance 208. The pulsing relay 210, which up to this time'has been held bythe relay 211, is now energized a circuit from battery through its winding,

lower front contacts of relay 209, thence overthetip'of the jack and plug, upper closed contacts of key 233 through the impulse'core tacts of the dial 225 to ground. As the dial restores to normal, the pulse relay210 releases andoperates repeatedly, in turn opening and closing the bridge across the con- 1" ductor 136 and 137 extending totheidistiant A At thetime, the trial; 15 Se a b ih'o'p rf ator and relay 204 operates *toshunt the re- 'sista'nce of the polarizedr-elays 212and 213," I I relay 126' at the local office energizes-and closes the circuit above traced for'the slow release relay-128. -Relay 128 at its innerleft' contact energizes thelowerwinding "of the right contact. of relay 128,-innerleft contact I however, does not operate.

of relay 126 toground, Relay 131 operates and locks to the groundedsconductor 143: f H 7 l Relay 126 also completes a loop: circuit ex tending over the branch 139.;EtotheIfirst se-f,"

lector Switch 3-1. This maybe traced frorn' conductor 152,' 'lo'wermost back contact=ofre lay 124, lower left winding of coil 123,-.neX't to the inner lower backcontact of relay 124, 7

upper windingof theelectro-polarizedErelay 125, resistance 154," outer contact ofrelay 126,

next to the inner upper back 'contact o f re lay 124, upper left Winding of coil' 123, upper-' most back contact of relay 124to conductor 153. This circuitlserves to'en-ergize' the usualimpulse relay attl1e-"selector switch-S 1."

Due to the direction of current fiow, how

ever, th'e rela'y125 will not operate.

otiice, relay 126 releases and 'closesa circuit from ground through its inner left'back'cone When: g

the first iinpulse is 'receivedfrom the central tact, middle left contact of relay 131, wind? .ing of relay 134 to battery. "Relay 134 ope'r' ates and excludes the right windings of the.

coil 123 from the. puls'eT circuit during dial} 7 At its outer contacts,relay.-126 repeats the impulsejto the selector switch s nl; The succeeding impulses are als'onrepeated; and the switches S1an:d C are operated to ex tend the connection to the called line 140.

7 Each time the dial returnsto' normal, relays 207 and 209 release, whereuponrelay 204 again moved away. from normal on" the suc ateand 1'clay204 againreleases'.

cord circuit. Relay remains operated.

When the called subscriber answers, cur-'1 rent is reversed in the branch-139 in theiistial manne'ryand relay 125 operates.' Relay 12 5" closes an obvious circuit-forrelay 1291' "Bei-l its I reoperjates." As soon,however, as tjh'ei dial is lay 129 operatesfand disconnects battery and ground from the trunkcircuit and holds the relay ,126fromreleasing. The removal 'o f battery and ground from the trunk circuit causes the releaseofrelay 204. Relay 204 closes 'a circuit for the-'supervisoryrelay 223' it extending from battery-through the coil 221,

relay 223:,thence over the. ring of the plug and jack, right contact of relay 204, upper front. contact of relay 203, coil 205, upper back contact of relay 20.7 over the tipof the jack and '5, plug to. ground at the coil '22 Relay 223.

. I extinguishes the. lamp 232-, advising the op.-

' 29 'Whas iS- Claimed i 1,, In. a telephone syste1n,linesof different classes, a trunk circuit consisting; of two. con- CllikCtOIS, nonsnumerical switches for connect-.

ingi lines. of one class directlyte said trunk,

nemmjicelly operated switches forconnect.

lines o fi another clas to; said trunk, and

' eans cont ol edoyer said trunk tor iving difierent; kinds of signals according to the class; o l ne onnected to the trunk.

a: 2. lira, teleplwisrew systenya local station,

at dif er nt. classes.- termina ing in. said station, a dis an St tion, runk interconnecting sai statiees, aourniimerical switches QQQIAGQQlJgg-thg Lines of one, class directly 7 trees, Clirectiw-ly' per ble switches ero nect g l es an ther lass to. sa trash. e. gnal fer a d trunkat th I station, nd: means at. he ca statip eiieetiye ac erc ingz t h las of; th seee iaec l to sa said Signal h g ve 3. In telephon ys em, al: ta ion was a i taststa eei a s of f ent las e tel-urinating in;v said localstation trunk; in-

#1 fi we i ieg aid ation w tch per trn k for contr ing tire esponsive to the' l t at on of a l n;

l nes ofi certain, class for conneeting said C i- FQQQX 9- tru-ilk; at the local sta tier. witches ntr lled d r ct v ly; 051 the lines. of another class for connecting such other li es to: r -e s ig l. fo e trunk at the distant station, and means fior operating a distinctive 1112111 nr according to Whether a callingline is & connected, to: the trunk automatically or di ec ir ly Y r *4. Ina'telep onesystem, alocalstatiomfa:

v distant oifice,'a lillll lk interconnecting said oca tation emlclistaat fice,. i s f be e r; classes, a s gnal ass ia with. ts

I, tmli li ll}. the distant; e ifice, lion-numerical; w ie es 0 eqnm i lg he in f; o e lass diss d-oz a 'ds wil at the l al a on,-

d ili cfiiively e19 able Swit he tor.- connecting W!- hess cf: amt ss s sa d runk:

' cations. 5. In a telephone system, a first statlom activ ndicatien local station a signal circuit. including the talking conductors of saidtrunk, and meansat the. local station for controlling said G.1.I-'

cuit in different Ways accordingto the class of the calling linesfor causing said signal.

at the distant office to give distinctive indi lines. of different characterthereat; a second station, a trunk interconnectingsaid stations, means responsive to the initiationof acall:

on a line of one character for connecting said line directly to, said trunk atthefirst; station, means controllable-. directive'ly'v overa calling hue of, another characterfoncon-i meeting such. line to said trunk 'la signal as sociated with said trunk; at-th-e second sta,

tion, a signal circuit including; thetalk i lgl conductors. of said trunk, ancl'm ans at the first station rendered efiective when. a line 0.15

a certain class calls for successively. inter-J rupting said signal circuit to: cause-the; int r-1:

mittent operation of the signal a.t.thedista1it;

end of the trunk;

6- In a lephone system, lines ofditlerent;

classes, a trunk, non-numerical switches for connecting the lines of oneclass directly .tOr

one endof said trunk, numerical swit hes for connecting the lines of another class-to. said end of said trunlg; a signal associatedwsrfith the other'end ofsai-d trunk, a. signal circuit. including the talking onductors. at sa trunk, means. responsive to. the extension off a. connection through a numerical switch; f r closing said, signal circuit; to cause-such sig;

ml to] operate steadily; and: means; ma en-1 sive to. the extension ot a connection through a non-uuc ierical witch for repeated y nte rupt ng aid signal. r ui t cause. the to operate internrittently. r

1.1. te ephonesystcm. tr nk i e, th

el phone lines each, f ifi icla s a;

e witch, tor Conn c ng on 1me di ect y s d tru k, 2 ine swi and a electer sw c fe n t ng th other in to said tr k.,, a, ingle ignal a ociatediw th said;

tfikl ea re ponsi etoa onnection through the line switch to said trunk; for.

ausing th pcrs cn: sa d ig a in a. dis.-

timee manner, andmeans, responsiveto connection throng-h a line switch a selecsw ch f x-c u ing th pe ati n said signal in a; different manner. I V 8. In a telcphonesysten a coin-controlled line fiat-rate 1151 6, a trunk circuit, a

numerical switch for connecting-said coin-.

controlled line directly to oneend; oi? said? trunk circuit, selector switch controlled over said, flat-rate line; for connecting such; line to the same end of said trunkcircuit, .a single signal thje'othcr end or said trunk circuit, and meanscontrolled over said. trunk for operating said signal distinctively ac cordung: to wln'clrline is con-nected-to the trunk g 9. In a telephone system, a local oiiice, linesof diiierent character terminating thereima central oifice having a manual operators position therein, a plurality of trunks 1nter-,

connecting said olfices, signal lamps at said pos tion, one for each of said trunks, nonnumerlcal switches for connectlng the lines of one class directly to said trunks at the lo-j cal'office, directively operable switches for selectively connecting the lines of another class to said trunks at the local oiiice, and means controlled over said trunks." in accordance with the class of the lines connected thereto at the local oifice for operating the said signals in a distinctive manner. 7

10. In a telephone system, a local office,

lines of different classes terminating therein,

r a distant otfice, a two-conductor trunk in- 'rectively operable switches for connecting terconnecting said oflices, non-numerical switches for connecting the llnes of one class directly to said trunk at the local oiiice, d1-

the lines of another class tosaid trunk atlthe local oflice, a signal for said trunk at the distant otfice, and means controlled over said trunk in accordance with the class of the line connected thereto for operating said sig nal in a distinctive manner.

11. In a telephone system, a first ofiic'e, lines of ditlerent classes terminating in said oflice, a second oflice, a trunk interconnecting said oiiices, non-numerical switches for connecting the lines of one class to said trunk at the first office, directively operable selector switches for connecting the lines of another class to said trunk at the first office, a signalvv at the second ofiice, means controlled over the trunk according to the class of line connected thereto at the first oflice for operating said I signal in a distinctive manner, and means at the second otfice for extending .a connection over'said trunk to the first ofiice.

'12 In a telephone system, a local otfice, two telephone lines terminating therein, a distant oflice, a trunk interconnecting said oflices, a line switch for connecting-one of said lines directly to said trunk at the local oiiice, a di rectively operable switchfor connecting the other line to said trunk at the local oifice, means at the distant ofice for extending a connection originating at the local office in the direction of a called line, a signal at the distant oflice, means dependent upon which line is connected to the trunk at the local office for operating said signal in a distinctive manner, an automatic switch at the local office, and means at said second ofiice for op erating said automatic switch over said trunk to extend a connection from the distant oflice in the direction of a called line in said local In witness whereof-,1 hereunto subscribe i my name this 14th day of February, 1930.

ROBERT CLJPAINE. 

